Project description:Purpose: The goals of this study were to identify cell specific expression patterns of the retinal pigment epithelium (RPE) and a variety of choroidal cell types originating from the macula and the periphery of human donor eyes, with a particular emphasis on identifying expression signatures of choroidal endothelial cells. Methods: Independent libraries were prepared for macular and peripheral samples of combined RPE/choroid from seven donors in two single cell sequencing experiments. In the first experiment, 8-mm macular and peripheral punches of RPE/choroid from Donors 1-3 were digested in papain prior to cryopreservation and subsequent GEM barcoding/library construction. Donors 1-2 had no noted ophthalmologic disease documented, while Donor 3 was diagnosed with age-related macular degeneration. In the second experiment, 12-mm macular and peripheral punches of RPE/choroid from Donors 4-7 were digested in collagenase II prior to cryopreservation, CD31-magentic bead enrichment and subsequent GEM barcoding/library construction. Donors 5-7 had no noted ophthalmologic disease documented, while Donor 4 was diagnosed with age-related macular degeneration. In both experiments, libraries were sequenced on a HiSeq4000. Sequenced reads were mapped to the human genome build hg19 will CellRanger(v3.0.1) and filters removed cells likely to be doublets or cells with a high proportion of mitochondrial reads. Clustering of cells with similar expression profiles was performed with Seurat (v3.0.2). Results: In the first experiment with unenriched RPE/choroid from donors 1-3, we recovered 4,355 cells post filtering with 40,177,477 corresponding reads. A total of 2,167 cells originated from the macula and 2,168 cells originated from the periphery. A total of 11 clusters were identified, and highly enriched genes in each cluster were used to classify clusters into their presumed dominant cell type. Differential expression analysis was performed between cells of macular and peripheral origin in each cluster and between donors with and without a history of age-related macular degeneration. Results: In the second experiment with CD31-enriched RPE/choroid from donors 4-7, we recovered 14,234 cells post filtering with 135,742,297 corresponding reads. A total of 7,647 cells originated from the macula and 6,587 cells originated from the periphery. A total of 8,521 of these cells were presumed endothelial cells. A total of 13 clusters were identified, and highly enriched genes in each cluster were used to classify clusters into their presumed dominant cell type(s). Differential expression analysis was performed between cells of macular and peripheral origin in each cluster and between donors with and without a history of age-related macular degeneration. Within each of the endothelial clusters (Clusters 5-8), differential expression analysis was performed between each cluster and the remaining endothelial cells. Conclusions: This study provides a large atlas of single-cell level gene expression patterns of the human retinal pigment epithelium and choroidal cell types. We identify expression patterns of most expected choroidal cell populations and describe macular versus peripheral regional differences. We additionally identify enriched transcripts in specific cell populations in age-related macular degeneration. We characterize gene expression patterns along the choroidal vascular tree, and identify populations of arterial, capillary, and venous endothelial cells. Our results show that single-cell sequencing can be performed on human RPE/choroid after cryopreservation, and that CD31 magnetic bead enrichment can be employed to enrich for endothelial cells for single-cell sequencing.

Project description:Proper spatial differentiation of retinal cell types is necessary for normal human vision. Many retinal diseases, such as Best disease and male germ cell associated kinase (MAK)-associated retinitis pigmentosa, preferentially affect distinct topographic regions of the retina. While much is known about the distribution of cell types in the retina, the distribution of molecular components across the posterior pole of the eye has not been well-studied. To investigate regional difference in molecular composition of ocular tissues, we assessed differential gene expression across the temporal, macular, and nasal retina and retinal pigment epithelium (RPE)/choroid of human eyes using RNA-Seq. RNA from temporal, macular, and nasal retina and RPE/choroid from four human donor eyes was extracted, poly-A selected, fragmented, and sequenced as 100 bp read pairs. Digital read files were mapped to the human genome and analyzed for differential expression using the Tuxedo software suite. Retina and RPE/choroid samples were clearly distinguishable at the transcriptome level. Numerous transcription factors were differentially expressed between regions of the retina and RPE/choroid. Photoreceptor-specific genes were enriched in the peripheral samples, while ganglion cell and amacrine cell genes were enriched in the macula. Within the RPE/choroid, RPE-specific genes were upregulated at the periphery while endothelium associated genes were upregulated in the macula. Consistent with previous studies, BEST1 expression was lower in macular than extramacular regions. The MAK gene was expressed at lower levels in macula than in extramacular regions, but did not exhibit a significant difference between nasal and temporal retina. The regional molecular distinction is greatest between macula and periphery and decreases between different peripheral regions within a tissue. Datasets such as these can be used to prioritize candidate genes for possible involvement in retinal diseases with regional phenotypes. Reprinted from <a href="https://www.ncbi.nlm.nih.gov/pubmed/?term=25446321">Whitmore, S.S., Wagner, A.H., DeLuca, A.P., Drack, A.V., Stone, E.M., Tucker, B.A., Zeng, S., Braun, T.A., Mullins, R.F., Scheetz, T.E., 2014. Transcriptomic analysis across nasal, temporal, and macular regions of human neural retina and RPE/choroid by RNA-Seq. Experimental Eye Research</a>. Used under <a href="http://creativecommons.org/licenses/by-nc-sa/3.0/">Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported </a>license. Additional RNA sequencing was performed on temporal, macular, nasal, inferior, and superior retina from a fifth subject and is included in this dataset. See original publication for details.

Project description:Purpose: Age-related degeneration (AMD) is a major cause of blindness in developed countries. The molecular pathogenesis of early events in AMD is poorly understood. We investigated differential gene expression in samples of human retinal pigment epithelium (RPE)/choroid from early AMD and control maculas using exon-based arrays. Methods: Gene expression levels in nine early AMD and nine control human donor eyes were assessed using Affymetrix Human Exon ST 1.0 arrays. Two controls did not pass quality control and were removed. Differentially expressed genes were annotated using DAVID, and gene set enrichment analysis (GSEA) was performed on RPE-specific and endothelium-associated gene sets. CFH genotype was also assessed and differential expression was analyzed with respect to high AMD risk (YH/HH) and low AMD risk (YY) genotypes. Results: Seventy-five genes were identified as differentially expressed (raw p-value < 0.01; >50% fold change, mean log2 expression level in AMD or control M-bM-^IM-% median of all average gene expression values); however, no genes were significant (adj. p-value < 0.01) after correction for multiple hypothesis testing. Of 52 genes with decreased expression in AMD (fold change < 0.5; raw p-value < 0.01), 18 genes were identified by DAVID analysis as associated with vision or neurological processes. GSEA of RPE-associated and endothelium-associated genes revealed a significant decrease in genes typically expressed by endothelial cells in the early AMD group compared to controls, consistent with previous histologic and proteomic studies. Analysis with respect to CFH genotype indicated decreased expression of ADAMTS9 in eyes with high-risk genotypes (fold change = -2.61; raw p-value = 0.0008). Conclusions: GSEA results suggest that RPE transcripts are preserved or elevated in early AMD, concomitant with loss of endothelial cell marker expression. These results are consistent with the notion that choroidal endothelial cell dropout occurs early in the pathogenesis of AMD. Using AltAnalyze (ver. 2.0.7 beta), we analyzed nine early AMD and nine control eyes using Affymetrix Human Exon ST 1.0 arrays. Following initial processing in AltAnalyze, two control arrays were identified as potential outliers by tests implement in arrayQualityMetrics, a package for R.

Project description:Dogs are commonly used models of human inherited retinal disorders. Because the dog retina contains a macula-like region, dogs are susceptible to maculopathies with many shared genetic etiologies with humans. Human macular gene expression has been characterized and provides insight into the underlying basis of macular disease. We sought to compare macular gene expression profiles in dogs and humans and interrogate macular disease-associated genes for differential expression between macula and periphery. RNA sequencing was performed on 8mm samples of the dog macular region and superior peripheral region, sampling retina and retinal pigmented epithelium/choroid separately. Read sequences were mapped to CanFam3.1 and raw read counts were analyzed to determine significantly differentially expressed genes between macula and periphery within each tissue. A similar analytic pipeline was used with a published dataset of human samples to allow direct dog/human comparisons. Pathways and processes involved in significantly DEGs were identified using the Database for Annotation, Visualization and Integrated Discovery. Dogs and humans shared the extent and direction of macular retinal differential gene expression, with multiple shared biological pathways implicated in differential expression. There were fewer similarities between dog and human in the supporting tissues of the retina (the RPE, choroid, sclera). Many genes implicated in heritable retinal and macular disorders in both dogs and humans were differentially expressed between macula and periphery. Approximately 2/3 of genes associated with human age-related macular degeneration were differentially expressed in at least one human tissue, whereas approximately half were differentially expressed in at least one dog tissue. This work underpins the dog macular retinal region as analogous to the human macula in terms of differential gene expression. Whilst age-related maculopathy has not been described in dogs, evidence supports the study of aging of the macula and susceptibility to age-associated pathology in dogs.

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Integration of eQTL and single-cell transcriptomics in the human eye identifies causal genes for age-related macular degeneration

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